PS Audio Power Plant 15........

For those who suggest a "settle in" period, thanks -- that's good to know. I've heard that with other things like cables, interconnects, etc. It's not clear to me where those elements are "burning in" or "settling" (as the lingo goes) vs. the other factor -- our ears getting used to a new setup. Indeed, it seems nigh impossible to disambiguate which is "us" and which is "the gear."

In a way, that's a problem, because we don't want to pay big $$ to get used to something that isn't really changing.

On the other hand, if the final experience is better, who cares? Better is better. (Of course, we're left with a question....)

The Power Plant thing is like any other piece of equipment- YMMV. Subjective "improvement".

I  instantly heard the opposite when I plugged a Power Plant in years ago. My 13 year old, PP Premier was recently refreshed by PS Audio and will go at least another 10 years. Best purchase I've made here on Agon.

I plug everything(including amp)into it with great results. 

I went from a Niagara 1200 to PS Audio P12 and the difference was stunningly improved.  I'm almost wondering if the OP is finding some levels of incoming THD euphonic in his system.  The P12 dropped incoming THD levels from 4% to 0.1% in my system.  The background became deeply black and quiet, particularly impactful with all my tube gear.

I can’t imagine what’s going on. The P15 has brought great improvement to my system too, especially with the performance of the DACs I have connected to it.

Break in... ? the op said it was a dealer demo, so it probably has many hours of playing time. But, it may need time to settle in its new environment. (perhaps a few hours).

I owned many iterations of PS Audio power conditioners, when I switched to the Niagara 7000 it was leap years better than PS Audio. Especially the fact that amps can be plugged into the Niagara! I now own in addition to the Niagara 7000 a 1200 that I use with my JL Subs and a 1000 that I use with my home theater equipment.

ozzy